This invention relates to a pipeline plug or packer for plugging a pipeline, such as a crude oil pipeline, at a selected location therealong.
Pipeline packers of the type to which the present invention relates are designed to act as positionable shut-off valves inside a pipeline. The packer is typically loaded into the pipeline through a standard pig trap and the packer is transported along the pipeline by the fluid flowing in the line. Tracking of the packer is typically done from above ground with a sensor receiving signals from a transmitter located on the packer. When the packer reaches the desired position, the pipeline pumping equipment is stopped to stop the flow and the packer is activated by remote control so as to seal the pipeline at that location. With two packers spaced some distance apart, it is possible to isolate a section of the pipeline, thereby allowing that section of the pipeline to be drained to provide a substantially liquid-free environment without draining the entire line. After the desired work in the pipeline has been accomplished, the packer is released by remote control, and the flow through the pipeline is started up to move the packer along the line with the packer being thereafter removed through a further pig trap.
The pipeline packer must be capable of forming a reliable seal under a wide variety of conditions. In mountainous country, extremely high pipeline hydrostatic heads are common, typically being in the order of several hundred pounds per square inch and, in extreme cases, pressure heads as high as 700 pounds per square inch may be encountered.